LIBKAKY 

UNIVERSITY  OF  ILLINOIS 

URBANA 


Field  Museum  of  Natural  History. 

Publication  159. 

Geological  Series.  Vol.  IV,  No.  2. 


NEW  OR  LITTLE   KNOWN   TITANOTHERES 

FROM  THE   LOWER  UINTAH 

FORMATIONS 

With  Notes  on  the  Stratigraphy  and  Distribution  of  Fossils. 


by- 
Elmer  S.  Riggs 
Assistant  Curator  of  Paleontology. 


Oliver  Cummings  Farrington, 
Curator,  Department  of  Geology. 


Chicago,  U.  S.  A. 

June,  1912. 


NEW    OR    LITTLE    KNOWN    TITANOTHERES   FROM   THE 
LOWER   UINTAH   FORMATIONS 

WITH    NOTES  ON  THE  STRATIGRAPHY  AND   DISTRIBUTION   OF   FOSSILS 


BY   E.   S.   RIGGS 


In  the  summer  of  1910  the  writer  was  authorized  by  the  Museum 
to  make  an  expedition  into  the  Uintah  Basin  of  northeastern  Utah  for 
the  purpose  of  collecting  vertebrate  fossils.  Accordingly,  a  party  con- 
sisting of  Mr.  J.  B.  Abbott  of  the  Museum  and  Mr.  M.  G.  Mehl,  a 
student  of  the  University  of  Chicago,  was  organized.  This  party  pro- 
ceeded by  way  of  Dragon,  Utah,  thence  overland  to  Vernal,  where  the 
necessary  equipment  and  supplies  were  obtained.  A  camp  was  then 
established  near  Well  2  at  the  foot  of  Coyote  Basin.  Six  weeks  were 
spent  in  working  the  exposures  within  driving  distance  of  this  camp, 
after  which  a  "dry  camp"  was  pitched  at  the  margin  of  White  River 
Canyon.  From  this  base  work  was  continued  in  the  exposures  of  the 
canyon  wall  during  the  remainder  of  the  summer.  Great  difficulties 
were  experienced  on  account  of  the  scarcity  of  water  and  feed  for  horses, 
and  on  account  of  the  extreme  hardness  of  the  formation.  In  excavat- 
ing fossils  the  use  of  drills  and  blasting  materials  was  often  necessary. 

The  result  of  this  expedition  was  a  large  collection  of  skulls,  jaws, 
and  two  partial  skeletons  belonging  to  the  family  Titanotheridce.  This 
family  is  represented  in  the  collection  by  the  genera  Mesatirhinus, 
Metarhinus,  Dolichorhinus,  Rhadinorhinus  and  Sthenodectes.  A  special 
interest  attaches  to  representatives  of  the  first  four  genera  because  of 
the  more  complete  representation  of  their  Uintah  species  and  the  inter- 
relationship of  the  genera  which  the  collection  brings  out.  Many  of 
these  species  were  obtained  from  a  lower  fossil-bearing  horizon  which 
has  hitherto  been  little  explored.  Other  genera  represented  in  the 
collection  are  Eobasileus,  Uintatherium,  Amynodon,  Triplopus,  Pro- 
telotherium,  Protyhpus,  Stylinodon,  Mesonyx  and  Harpagalestes. 

The  genus  Rhadinorhinus  is  new,  Mesatirhinus  and  Stylinodon  are 
for  the  first  time  reported  from  the  Uintah  formations,  and  Eobasileus 
is  first  reported  from  skulls  capable  of  identification. 

STRATIGRAHPY 

The  Uintah  formations,  or  " Uintah  Group,"  were  primarily  sub- 
divided by  the  U.  S.  Geological  Survey  upon  an  evident  change  in  the 
lithological  structure  of  the  beds.     This  division  separated  the  lower 

17 


18    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

brown  sandstones  from  the  upper  red  clays.  The  lower  series  was 
designated*  by  C.  A.  White  as  Bridger  and  treated  as  a  continuation  of 
that  series  from  the  better  known  Bridger  Basin.  The  upper  series  was 
designated!  by  King  as  true  Uintah.  The  lower  series  was  further 
subdivided!  by  Peterson  into  two  horizons  designated  as  A  and  B ,  while 
the  upper  series  or  true  Uintah  was  designated  as  horizon  C. 

The  correlation  of  the  Uintah  formation  with  other  Tertiaries  has 
proceeded  slowly  as  evidence  has  from  time  to  time  been  adduced  from 
itc  fossil  fauna.  The  fauna  has  hitherto  been  best  known  from  the 
middle  and  upper  measures.  Scott,  in  his  admirable  monograph  on 
the  Mammalia  of  the  Uintah  formation,  concludes  by  pointing  out  its 
affinities  with  the  Bridger,  or  middle  Eocene,  fauna.  At  the  same  time 
he  confirmed  the  generally  accepted  view  that  the  Uintah  group  should 
be  placed  at  the  summit  of  the  Eocene,  forming  the  transition  to  the 
White  River  Miocene.  Osborn,  in  his  "Age  of  Mammals,"  has  put 
forth  a  careful  series  of  correlations  between  the  Bridger  and  Washakie 
horizons  on  the  one  hand  and  the  Uintah  formation  on  the  other. 

It  is  the  purpose  of  this  paper  to  bring  out  a  little  known  titanothere 
fauna  from  the  middle  and  lower  horizons  and  to  add  something  in 
detail  concerning  the  range  of  various  fossil  forms.  In  connection  with 
this  the  following  notes  on  the  stratigraphy  of  the  Lower  Uintah  Beds 
are  offered  in  order  to  more  clearly  define  the  known  range  of  these 
forms. 

The  subdivision  of  the  Lower  Uintah  Beds  has  been  somewhat 
vague,  owing  to  the  absence  of  strata  which  could  be  defined  or  traced 
through  any  considerable  distance.  As  will  be  seen,  the  sandstone 
systems  are  chiefly  of  fluviatile  origin  and  though  often  numerous  and 
massive,  the  ledges  are  of  limited  lateral  extent.  They  therefore  offer 
no  well  marked  datum -planes.  These  heavy  ledges  of  river  sandstones 
are  the  chief  fossil-bearing  horizons  of  the  lower  Uintah.  Being  often 
separated  by  long  barren  stretches,  it  is  only  with  great  difficulty  that 
fossil-bearing  levels  can  be  traced  from  one  locality  to  another.  It 
therefore  appears  necessary  to  base  the  subdivisions  upon  faunal  dis- 
tribution —  the  method  resorted  to  in  nearly  all  inland  Tertiaries. 
While  employing  this  method  of  subdivision  the  present  writer  will 
depart  from  the  accepted  classification  only  so  far  as  is  necessary  in 
making  clear  distinctions. 

The  White  River  Canyon  offers  the  most  favorable  opportunity  for 
examining  the  strata  of  the  lowermost  Uintah  horizon.     A  fissure 

*  Hayden  Survey,  1876,  p.  37. 

fU.  S.  Geological  Exploration  of  Fortieth  Parallel,  Map  1. 

§  Bull.  Amer.  Mus.  Vol.  VII,  pp.  72-74. 


June,  1912.  New  Titanotheres  —  Riggs.  19 

deposit  of  Gilsonite^  which  cuts  deep  into  the  canyon  wall  three  miles 
below  the  mouth  of  Evacuation  Creek  and  extends  some  miles  to  the 
northwestward  offers  a  convenient  point  for  making  a  section.  Actual 
measurements  were  not  made,  but  the  contour  lines  of  the  U.  S.  Survey 
maps  made  it  possible  to  estimate  with  some  degree  of  accuracy  the 
vertical  dimensions.  Figure  1,  representing  this  section,  is  based  upon 
these  estimates. 

Lower  Metarhinus  Zone.  The  shaly  gray,  sandstones  of  lacus- 
trine origin  which  have  been  more  or  less  provisionally  referred  to  the 
Green  River  series*  dip  slightly  below  the  bed  of  White  River  at  this 
point.  Upon  these  shales,  with  no  very  evident  line  of  demarcation, 
lies  the  Uintah  Series.  The  lower  two  hundred  feet  of  this  series  is 
largely  made  up  of  friable,  sandy  shales,  interspersed  with  layers  of 
nodules  and  thin  ledges  of  sandstone.  Occasionally  these  shales  are 
interrupted  by  massive  ledges  of  sandstone  of  limited  extent.  The 
latter  are  usually  coarse-grained,  cross-bedded  in  places  but  in  the 
thicker  ledges  quite  homogeneous.  They  vary  in  color  from  a  light 
gray  in  the  thinner  layers  to  dull  brown  in  the  weathered  surfaces  of 
the  more  massive  ledges.  These  shales  weather  in  rather  steep  slopes, 
marked  by  the  horizontal  outcroppings  of  nodular  or  sandy  layers. 

Above  the  shales  at  this  point  lies  a  series  of  columnar  sandstones 
some  three  hundred  feet  in  thickness.  They  weather  in  the  form  of 
bold  cliffs,  standing  out  as  buttresses  along  the  canyon  wall.  (PI.  IV.) 
These  sandstones  consist  of  relatively  thin  ledges  of  fine-grained, 
often  calcareous,  sand  varying  somewhat  in  hardness  and  presenting 
rugged  bandings  in  the  face  of  the  cliff.  The  color  is  slightly  more 
grayish  than  the  underlying  shales  but  brown  predominates. 

This  lower  five  hundred  feet  of  the  Uintah  Formation  is  compara- 
tively barren  of  fossils.  Some  days'  search  in  the  vicinity  of  this  section 
revealed  only  occasional  fragments  of  turtle  shells.  Mammals  have 
been  found  in  these  measures  at  other  points  along  White  River.  The 
type  specimens  of  Metarhinus  and  of  Sphenocoelus  are  said  to  have  been 
collected  from  the  lower  levels.  The  first  has  never  been  duplicated, 
the  second  is  represented  by  a  fragment.  While  the  occurrence  of 
these  two  genera  in  the  lower  measures  is  a  matter  of  record,  the  rarity 
of  individual  representatives,  as  well  as  the  small  number  of  forms  found 
in  this  horizon,  may  justify  its  being  designated  as  relatively  barren. 

Upper  Metarhinus  Zone.  The  succeeding  four  hundred  feet  is 
made  up  chiefly  of  massive  ledges  of  sandstone  alternating  with  layers 
of  sandy  shales  or  indurated  clays.  The  sandstones  vary  in  thickness 
from  five  to  thirty  feet.     They  are  of  limited  extent,  usually  playing 

*  White,  Op.  cit. ;  Scudder,  Tert.  Insects. 


20    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 


Dolickorhinus  tongiceps 


Triplopus 
Dolickorhinus  tongiceps 


Dolickorhinus  tongiceps 
Metarkinus  earlei 


Mesonyx 
Triplopitf 


Rkadinorhinus  abkotti 
Type  locality 

Dolickorhinus  longicep* 
Metarkinus  cristatus 

Type  locality 
Metarkinus  riparius 
Eobasileus 
Dolichorhinns  tongtcepfi 


Metarkinus  riparinA 


Fig.  I.    Section  of  Metarhinus  Beds,  as  exposed  in  the  north  wall  of  White  River. 
See  pages  19  and  22. 


June,  1912. 


New  Titanotheres  —  Riggs. 


21 


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out  and  being  replaced  by  other  ledges  at 
slightly  different  levels.  The  thicker  ledges 
are  made  up,  for  the  greater  part,  of  fine- 
grained sands  firmly  cemented  by  calcareous 
material,  gray  when  freshly  broken  but 
weathering  to  a  reddish  brown.  In  every 
ledge  there  are  traces  of  cross-bedding, 
evidenced  by  diagonal  veins  of  coarser 
sands.  Near  the  base  or  above  a  second 
bedding  plane,  there  is  often  a  coarser  layer 
of  river  sand  containing  pebbles  of  quartzose 
materials,  sandstone,  and  clay  shales.  This 
layer  is  invariably  cross-bedded,  often  inter- 
rupted and  replaced  at  nearly  the  same  level. 
In  these  coarser  strata  occur  as  fossils  dis- 
articulated bones,  branches  and  sometimes 
trunks  of  trees.  In  the  upper  series  the 
sandstones  weather  into  vertical,  or  often 
over-hanging  walls,  with  accumulations  of 
fallen  blocks  at  the  base.  (PL  V,  Fig.  1.) 
In  the  lower  levels  they  are  quite  as  often 
exposed  in  steep  slopes  half  covered  with  a 
shaly  talus.  Many  of  the  calcareous  ledges 
disintegrate  where  exposed  to  the  weather- 
ing agencies  and  flake  away  more  rapidly. 
These  two  series,  designated  as  Lower 
and  Upper  Metarhinus  Zones,  include,  as 
nearly  as  the  writer  can  determine,  Horizon 
A  of  Peterson  and  Osborn.  Probably  they 
include  a  little  more  than  was  originally 
so  designated.  The  lower  division  is  best 
defined  as  including  the  whole  of  those  sand- 
stones in  which  the  genus  Metarhinus  occurs. 
This  genus  is  by  far  the  most  distinctive  fos- 
sil of  this  horizon  and  is  apparently  confined 
to  it,  though  at  certain  levels  Dolichorhinus 
was  found  equally  abundant.  In  the  three 
months  of  careful  work  and  record  by  our 
party  no  trace  of  Metarhinus  was  found 
above  the  sandstones  described.  However, 
the  habitat  of  this  animal  appears  to  have 
limited  its  occurrence  to  the  river  sands. 


22    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

Five  miles  up  the  canyon  from  the  line  of  this  section  a  single  ledge 
(PI.  V,  Fig.  i)  a  half-mile  in  extent  yielded  so  many  specimens  of  this 
genus  as  to  be  designated  by  our  collectors  as  the  Metarhinus  Sand- 
stone. However,  six  other  genera  of  mammals,  one  of  crocodile  and 
various  turtles  are  recorded  from  these  beds. 

The  term  "Telmatherium  megarhinum  Beds,"  originally  applied* 
to  this  series,  being  no  longer  applicablef ,  it  is  here  proposed  to  desig- 
nate the  series  as  the  Metarhinus  Beds,  in  honor  of  the  form,  which  was 
first  described  from  them  and  is  still  their  most  characteristic  fossil. 
The  beds  may  be  further  divided  into  a  Lower  and  an  Upper  Metar- 
hinus Zone  as  indicated  in  Figure  i. 

Amynodon  Beds.  Above  the  Metarhinus  Beds,  or  Horizon  A,  lies 
a  series  of  three  hundred  feet  of  shales  and  clays  including  occasional 
ledges  of  fluviatile  sandstone.  They  are  best  represented  some  five 
miles  farther  up  White  River  from  the  last  section.  At  this  point  the 
formation  is  exposed  in  the  more  open  country  in  a  series  of  eroded 
ledges  dipping  to  the  northwestward  at  an  angle  of  two  or  three  degrees. 
Gilsonite  Vein  No.  2,  which  extends  several  miles  in  a  northwesterly  di- 
rection from  the  canyon's  northern  edge,  may  be  taken  as  the  basis  of  the 
section  (Fig.  2).  This  vein  is  marked  by  a  series  of  mines  and  prospect 
holes  easily  recognized.  The  section  extends  from  the  canyon  rim  to  the 
mesa  bordering  Coyote  Basin  on  the  northward.  This  includes  sub- 
stantially the  same  vertical  series  as  Horizon  B  of  Peterson  and  Osborn 
so  far  as  the  writer  has  been  able  to  interpret  them. 

These  beds  are  composed  of  sandy  shales  and  brilliantly  colored 
clays  with  occasional  ledges  of  sandstone  and  included  lenses  of  more 
limited  extent.  The  series  is  capped  by  a  massive  ledge  which  appears 
at  the  brow  of  the  mesa  bounding  Coyote  Basin  on  the  northwest. 
This  may  fittingly  be  designated  as  the  Amynodon  Sandstone. 

Between  the  uppermost  ledge  of  the  Metarhinus  Beds  and  the 
Amynodon  Sandstone  lie  a  series  of  clays  and  lenticular  sandstones  of 
variable  character.  The  Metarhinus  Sandstones  are  succeeded  by  one 
hundred  feet  of  bluish  or  grayish  shales  including  thin  ledges  of  sand- 
stone. These  are  overlain  by  forty  feet  or  more  of  homogeneous  fine 
red  clays,  capped  by  a  ledge  of  sandstone  five  or  six  feet  in  thickness. 
Then  come  fifty  feet  of  dark  grayish  clays  including  lenticular  sand- 
stones of  rather  coarse-grained,  ferruginous  character.  These  sands 
weather  in  slopes  quite  as  flat  as  the  clays  in  which  they  are  included. 
They  are  rich  in  mammalian  fossils,  of  which  Dolichorhinus  longiceps, 

*  Bull.  Am.  Mus.,  Vol.  VII,  p.  95. 

t  The  specimen  alluded  to  was  later  made  the  type  of  Metarhinus  fluviatilis,  see 
Bull.  Am.  Mus.,  Vol.  XXIV,  p.  609. 


June,  1912.  New  Titanotheres  —  Riggs.  23 

Sthenodectes  incisivum  and  Amynodon  intermedins  were  recorded.  The 
remaining  seventy-five  feet  below  the  Amynodon  Sandstone  consist 
of  light  gray  or  greenish  clays  little  indurated  and  weathering  in  the 
form  of  typical  bad  lands.  These  contain  a  varied  fossil  fauna  but 
having  been  exploited  by  earlier  collectors,  little  attention  was  given 
to  them.  However,  specimens  of  Uintatherium  (?),  Stylinodon  sp., 
Amynodon  intermedins  and  Protylopus  were  recorded.  Capping  this  as 
the  "rim-rock"  of  the  basin  is  the  massive  Amynodon  Sandstone  before 
mentioned.  It  reaches  in  places  a  thickness  of  twenty  feet,  thins  out 
and  sometimes  disappears  entirely  but  is  replaced  again  by  a  similar 
ledge  at  approximately  the  same  level.  These  ledges  are  perhaps  the 
richest  in  vertebrate  fossils  of  any  horizon  noted.  Amynodon  and 
Crocodilus  are  common;  Protelotherium  uintense  also  was  found. 


RANGE  AND  OCCURRENCE  OF   FOSSILS 

Some  observations  upon  the  range  and  occurrence  of  fossil  mammals 
in  the  Lower  Uintah  formations  are  worthy  of  mention.  A  careful 
record  was  kept  of  the  exact  geological  horizon  of  every  specimen 
collected.  Attention  was  also  given  to  the  character  of  the  formations 
in  which  the  various  fossils  occur,  their  sequence  and  the  association 
with  plant  and  invertebrate  fossils,  in  order  to  throw  any  possible  light 
upon  the  condition  of  deposition  or  the  habits  of  the  animal.  The 
geological  distribution  as  indicated  in  Figs.  1  and  2  is  based  entirely  upon 
the  collection  made  by  this  expedition.  With  a  few  exceptions  the  data 
are  based  upon  material  sufficiently  complete  to  be  preserved  as  museum 
specimens  and  accurately  identified.  In  no  case  was  a  record  made 
from  fragments  not  in  situ.  The  Lower  Metarhinus  Zone  is  indicated 
as  relatively  barren. 

Five  genera  of  mammals  have  been  reported*  by  Osborn  from  the 
entire  Horizon  A.  Mr.  Peterson,  who  made  the  collection,  has 
assured  the  writer  that  the  type  specimens  of  Metarhinus  fluviatilis 
and  Sphenocoelus  uintensis  came  from  the  lowermost  levels  of  that 
horizon.  In  the  lower  zone  typical  fossil -bearing  ledges  occur,  but 
much  less  frequently  than  in  the  upper.  A  number  of  ledges  ex- 
amined by  our  party  proved  quite  barren.  In  the  upper  strata  frag- 
ments of  turtle  shell  were  noted.  It  is  quite  probable  that  somewhere 
in  these  channel  deposits  fossil-bearing  "pockets"  may  be  discovered. 
Upon  such  discoveries  rests  the  hope  of  further  light  upon  the  fauna 
of  the  Lower  Metarhinus  Zone.  The  sandy  shales  such  as  make  up  the 
larger  part  of  this  series  do  not  offer  conditions  favorable  for  the  preser- 

*  Bull.  Am.  Mus.,  Vol.  VII,  p.  75. 


24    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

vation  of  any  mammalian  fauna  which  may  have  found  its  way  into  the 
Uintah  basin  at  this  stage. 

Fossils  in  the  Upper  Metarhinus  Zone  are  found  almost  without 
exception  in  the  sandstone  ledges,  rarely  in  the  shales  which  alternate 
with  them.  Sometimes  they  occur  in  the  homogeneous,  fine-grained 
sandstone  but  more  often  they  are  confined  to  the  narrow,  coarse- 
grained, cross-bedded  layers  which  often  occur  near  the  base,  sometimes 
at  the  top,  of  massive  ledges.  Skulls  are  often  embedded  in  semi- 
gravelly  layers  and  have  their  narial  or  orbital  cavities  filled  with 
pebbles  which  could  be  carried  only  by  rapidly  flowing  water.  Another 
evidence  of  stream  action  lies  in  the  complete  dissociation  of  the  various 
skeletal  elements.  Seldom  are  the  lower  jaws  associated  with  the 
skulls,  or  so  much  as  two  vertebras  found  articulated.  There  are  ex- 
ceptional instances  where  whole  skeletons  are  found  but  little  disturbed. 
In  the  few  instances  noted  these  were  embedded  in  a  fine-grained, 
homogeneous  sandstone  apparently  deposited  in  more  quiet  water  such 
as  deep  pools  or  eddies. 

The  Upper  Metarhinus  Zone  presents  a  much  more  varied  fauna. 
It  includes,  along  with  the  low-ground  titanotheres,  a  number  of  forms 
whose  structure  indicates  greater  activity  and  which  may  have  inhabited 
woodlands  or  open  plains.  Throughout  this  series  there  appears  an 
ever-increasing  percentage  of  upland  forms.  The  titanothere  genera 
Metarhinus  and  Dolichorhinus  are  equally  well  represented.  Their 
fossil  remains  are  usually  found  associated  in  the  same  ledges  and 
apparently  deposited  under  the  same  conditions.  In  the  one  instance 
in  which  a  large  part  of  a  Dolichorhinus  skeleton  was  found  articulated, 
a  skeleton  of  a  young  Metarhinus  was  mingled  with  it  in  such  a  manner 
that  it  was  at  first  mistaken  for  the  young  of  the  same  form.  There 
is  one  notable  exception  to  the  parallel  occurrence  of  these  two  forms 
in  the  Upper  Metarhinus  Zone.  An  isolated  ledge  of  sandstone  repre- 
sented at  the  base  of  Section  2  (Fig.  2)  yielded  Metarhinus  skulls 
and  jaws  in  relative  abundance.  Four  specimens  of  M.  riparius 
and  three  of  M .  earlei  are  recorded  from  this  ledge  but  no  trace  of 
Dolichorhinus  was  found  in  it.  It  is  significant  that  such  titanotheres 
as  Telmatherium  and  Mesatirhinus  superior  also  occur  in  this  ledge. 
It  was  noted  also  that  Dolichorhinus  was  found  only  in  heavy  sandstone 
systems.  Apparently  this  animal  was  confined  to  the  vicinity  of  large 
streams. 

Other  genera  common  to  the  Upper  Metarhinus  Zone  are  the  more 
rare  and  probably  upland  Rhadinorhinus ,  the  gigantic  Eobasileus,  the 
small  hyracodont  Triplopus,  and  two  large  creodonts,  Mesonyx  and 
Harpagalestes.     Occasional  crocodiles  and  numerous  turtles  are  found, 


June,  1912.  New  Titanotheres —  Riggs.  25 

also  beds  of  fresh-water  clams.  Reeds,  leaves,  and  branches  of  trees 
are  abundant  in  the  upper  sandstone  in  association  with  representatives 
of  the  upper  fauna. 

The  Amynodon  Beds  represent  a  transitional  stage  both  in  their 
stratigraphy  and  in  the  characters  of  the  fauna.  The  river  sandstones 
rapidly  give  place  to  shales  and  clays.  Fossils  occur  in  the  heavier 
sandstones  very  much  as  in  the  Upper  Metarhinus  Beds;  at  the  same 
time  they  become  more  abundant  in  the  shales  and  clays  as  we  pass 
upward  in  the  series.  In  the  lower  sandy  shales  but  few  evidences  of 
mammals  are  recognized,  though  in  certain  narrow  strata  fragments  of 
Eobasileus  occur  with  comparative  frequency.  The  lenticular  sand- 
stones, apparently  of  quiet  water  deposition,  are  rich  in  the  remains 
of  low-ground  mammals  such  as  Amynodon,  Sthenodectes  and  Dolicho- 
rhinus.  These  sands  show  little  evidence  of  water  currents.  Skulls 
with  mandibles  and  parts  of  skeletons  are  found  associated. 

The  gray  clays  yield  a  mixed  fauna  of  lowland  and  plains  forms. 
Dolichorhinus  and  Amynodon  are  common;  other  genera  recognized 
are  Uintatherium  (?),  Stylinodon  and  Protylopus.  Little  attention 
was  given  to  these  beds.  It  is  probable  that  a  careful  search  would 
reveal  a  much  larger  number  of  fossil  forms  than  are  here  recorded. 
The  massive  sandstones  forming  the  upper  series  of  the  Amynodon 
Beds  yield  Amynodon  and  Dolichorhinus  as  the  most  characteristic 
fossils.     Protelotherium  and  Crocodilus  are  also  recorded  from  them. 

The  Upper  Uintah  Beds  (Horizon  C)  are  not  included  in  this  recon- 
noissance.  It  may  be  noted  that  this  series  is  ushered  in  by  an  even 
more  marked  transition  than  the  last.  Red  clays  and  friable  sand- 
stones predominate.  Massive  sandstones  are  rare  and  of  limited 
extent.  The  fauna  is  known  from  the  researches  of  Marsh,  Scott, 
Osborn,  Hatcher  and  Douglass. 

Subfamily  DOLICHORHIN^ 

Middle  Eocene  titanotheres  having  nasals  elongate  and  deeply 
recessed  laterally,  face  shorter  than  cranium,  an  infra-orbital  process 
more  or  less  developed,  and  molars  only  moderately  expanded. 

This  group  is  proposed  in  order  to  designate  those  long-nosed 
titanotheres  which  evidently  sprang  from  a  common  stock  and  form  a 
natural  and  homogeneous  group.     It  includes  the  following  genera: 
Mesatirhinus  Dolichorhinus 

Metarhinus  Rhadinorhinus 


26    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

Mesatirhinus*  Osborn. 

Type  species  M.  megarhinus  Earle. 

Range,  Bridger  C  and  D,  Washakie  A  and  B,  now  extended  to  include 
Uintah  A. 

The  generic  characters  may  be  modified  as  follows:  Skull  length  354- 
485  mm.,  frontals  relatively  narrow,  rounded  and  not  overhang- 
ing the  orbits,  sagittal  crest  progressively  reduced. 

M.  superior,  sp.  nov. 

Type  specimen,  No.  12 188,  Field  Museum.     (PL  VI.) 

Type  locality:   Upper  Metarhinus  Sandstones,'  White  River  divide. 

Specific  characters:  Skull  485x255  mm.,  molar  series  182  mm., 
nasals  free  to  a  point  over  last  premolar,  infra-orbital' process 
present,  arches  slender  anteriorly,  nasals  infolded  at  margins, 
sagittal  area  expanded,  canines  small,  P2  and  P3  oblique  to  axis 
of  series.  Molars  relatively  small,  strong  hypocone  on  M3, 
posterior  nares  opening  opposite  the  anterior  margin  of  last 
molar. 

This  genus,  reported  for  the  first  time  from  the  Uintah  formations, 
is  apparently  indigenous  to  the  Bridger  and  Washakie  basins.  It  is 
represented  in  the  Field  Museum  collections  by  a  single  specimen  —  an 
incomplete  skull  collected  by  Mr.  J.  B.  Abbott  from  the  top  of  the 
Metarhinus  Sandstones  near  Gilsonite  Vein  No.  2.  The  right  arch  is 
wanting,  together  with  the  basi-occipital  and  condyles.  The  dentition 
is  anatomically  complete  excepting  the  incisors. 

The  skull  presents  striking  similarities  with  the  earlier  representa- 
tives of  Dolichorhinus.  From  the  dorsal  view,  the  nasals,  facial  and 
supra-cranial  regions  appear  very  similar,  though  the  cranial  region 
does  not  have  the  pronounced  downward  curve  characteristic  of  Doli- 
chorhinus. In  the  palatal  view  more  marked  differences  are  noticeable. 
The  premolars  are  more  primitive,  the  molars  smaller,  and  the  posterior 
narial  opening  is  unmodified.  In  these  characteristics  the  specimen 
in  hand  resembles  D.  heterodon"\  from  Upper  Uintah  B  more  closely. 
However,  it  differs  from  that  species  in  having  a  strong  hypocone  on  the 
last  molar,  and  in  the  whole  facial  profile.  In  our  present  knowledge 
of  these  many  closely  related  forms,  this  species  may  be  regarded  as 
the  largest  and  most  highly  specialized  representative  of  Mesatirhinus: 
Further  measurements  of  the  type  specimen  are  given  on  page  39. 

*  Bull.  Amer.  Mus.,  Vol.  XXIV,  p.  608,  1908. 

t  Douglass,  Annals  Carnegie  Museum,  Vol.  VI,  p.  810,  1909. 


June,  1912.  New  Titanotheres —  Riggs.  27 

Metarhinus   Osborn 

The  genus  Metarhinus  is  based  upon  a  series  of  specimens  from  the 
Uintah  Metarhinus  Beds.  It  has  for  its  type  a  skull  (Am.  Mus.  No. 
1500)  from  the  lowermost  horizon*  of  these  beds.  Two  other  species, 
M.  earlei  and  M.  diploconus  have  been  referred  to  this  genus. f  The 
former  species  from  the  Upper  Washakie  Beds  is  recognized  from  the 
Upper  Metarhinus  Beds  of  the  Uintah.  The  differences  between  the 
type  of  M.  diploconus  and  other  species  more  directly  in  line  with  the 
generic  type  appear  to  warrant  its  removal  from  this  genus.  § 

The  Field  Museum  collection  includes  a  more  complete  series  of 
specimens  referable  to  Metarhinus  than  has  hitherto  been  known. 
Among  these  are  seven  adult  skulls,  and  one  of  a  young  individual, 
together  with  two  associated  and  various  isolated  mandibles.  These 
specimens  come  from  higher  levels  and  represent  more  advanced  stages 
of  development  than  the  type  species. 

From  a  comparative  study  of  all  the  materials  referred  to  Metarhinus 
the  genus  may  be  characterized  as  follows: 

Type  species,  M.  fluviatilis.% 

Range:  Uintah  Metarhinus  Beds  (Horizon  A)  and  Washakie  B. 
Generic  characters:  Small  titanotheres  (skull  length  355-415 
mm.)  having  orbital  region  unusually  prominent,  nasals  expanded 
distally  and  free  to  a  point  above  the  anterior  margin  of  the  orbit, 
incipient  horn-cores  at  fronto-nasal  suture,  posterior  nares  open- 
ing opposite  second  molar,  sagittal  crest  more  or  less  reduced, 
molars  with  low  crowns,  hypocone  on  M3  present  or  reduced. 
Mandible  with  narrow,  straight  ramus,  first  lower  premolar 
single-rooted  or  absent. 

The  genus  includes  two  phyla,  which  are  apparently  distinct  but  so 
far  as  is  now  known  merit  no  more  than  specific  rank.  The  first  phylum 
includes  M.  fluviatilis  from  the  Lower,  and  M.  riparius  from  the  Upper 
Metarhinus  Beds.  These  are  clearly  indigenous  types  known  from  the 
Uintah  only.  In  their  dental  characters  they  are  the  more  primitive. 
The  canine  is  large,  the  premolars  more  diagonal  and  the  hypocone  on 
M3  present,  often  prominent.  The  molars  in  adults  are  usually  deeply 
worn.  The  second  phylum  includes  forms  relatively  short-headed, 
broad  in  the  frontal  region,  with  more  rectangular  premolars,  broad 

*  Fide  Peterson. 

t  Bull.  Amer.  Mus.,  Vol.  XXIV,  p.  610. 

§  Vide  infra. 

t  Bull.  Amer.  Mus.,  Vol.  XXIV,  p.  609,  1908. 


28    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

faced  molars  usually  little  worn  in  the  adult  and  with  no  trace  of  a 
hypocone  in  M3.  The  earlier  forms  of  both  phyla  have  high  sagittal 
crests.  The  expanding  cranial  areas  in  the  more  advanced  forms 
develop  differences  which  become  more  and  more  evident. 

Metarhinus  fluviatilis,  Osborn.*     Type  of  genus. 

Type  specimen,  No.  1500  Amer.  Mus. 

Type  locality,  base  of  Metarhinus  Beds,  White  River  Canyon. f 
This  is  much  the  smaller  and  more  primitive  species  of  the  genus. 
It  may  be  readily  distinguished  by  the  small  size  (355x200  mm.),  the 
short  basi-cranial  region,  the  long  sagittal  crest  and  the  prominent 
hypocone  on  M3.  No  specimen  referable  to  this  species  was  secured  by 
the  Field  Museum. 

Metarhinus  riparius,  sp.  nov. 

Type  specimen,  No.  12 186  Field  Museum.      (PI.  VII,  Fig.    1). 

Range:  Entire  Upper  Metarhinus  Beds,  White  River  Canyon  and 
divide. 

Specific  characters:  Skull  long  and  narrow  (405x210  mm.).  An- 
terior cranial  region  expanded,  sagittal  crest  short.  Inter- 
orbital  region  relatively  narrow  and  rounded,  rudimentary 
horn-cores  above  orbits,  canines  large,  molar  series  short  (88-93 
mm.),  hypocone  usually  present  on  M3,  mandible  straight  in  the 
ramus,  lower  canine  long  and  recurved. 

This  is  the  most  common  species  in  the  Metarhinus  Beds.  Four 
skulls,  two  associated  lower  jaws  and  one  isolated,  in  the  Field  Museum 
collections  are  referred  to  it.     (Nos.  12174,  12183,  12191,  12195,  12196.) 

Metarhinus  cristatus,  sp.  nov. 

Type  specimen,  No.  12194  Field  Museum.     (PI.  IX,  Fig.  3). 

Type  locality:  Upper  Metarhinus  Beds  (Horizon  A),  White  River 
Canyon. 

Specific  characters:  Skull,  length  approximately  380  mm.,  molar 
series  94  mm.  Frontal  region  broad,  sagittal  crest  long  and 
high,  molars  short-crowned,  no  hypocone  on  M3,  arches  rela- 
tively heavy.  Represented  by  a  single  skull  lacking  the  nasals 
and  the  premaxillaries. 

*  Bull.  Am.  Mus.,  Vol.  XXIV,  p.  609,  1908. 
f  Fide  Peterson. 


June,  1912.  New  Titanotheres  —  Riggs.  29 

Metarhinus  earlei*  Osborn. 

Type  specimen,  No.  13 166  Amer.  Mus. 

Type  locality:   Washakie  B  and  Upper  Metarhinus  Beds  (Horizon 

A). 
A  splendid  skull  (No.  12 187,  Field  Museum,  PI.  VIII),  two  mandibles 
(Nos.  1 21 78  and  12 189)  and  a  distorted  skull  (No.  12 169),  all  from  the 
uppermost  Metarhinus  Sandstones,  are  referred  to  this  species.  From 
these  referred  specimens,  as  well  as  from  the  type,  the  following 
characters  are  derived: 

Skull,  short  and  broad  in  frontal  region,  length  388-405  mm.,  breadth 
245-255  mm.  Molar  series  broad  and  low-crowned,  no  hypocone 
on  M3;  linea  aspera  uniting  by  regular  curves  above  posterior 
margins  of  zygomata  to  form  a  short,  thickened  sagittal  crest; 
canines  slender,  diastema  short,  P2  oblique,  P3  and  P4  sub- 
rectangular  in  outline,  molars  broad  and  low-crowned,  no  hypo- 
cone  on  M3,  mandible  with  ramus  slightly  curved. 

Metarhinus  represents  a  rapidly  expanding  and  comparatively  short- 
lived group.  Its  known  vertical  range  in  the  Uintah  is  less  than  one 
thousand  feet.  As  before  indicated,  the  genus  early  divides  into  two 
lines  which  run  parallel  through  the  greater  part  of  Horizon  A  and 
disappear  at  the  top  of  the  heavy  river  sandstones.  In  general  these 
two  phyla  may  be  characterized  as  the  broad-headed  and  the  narrower- 
headed  forms. 

There  is  a  considerable  increase  in  size  between  the  earlier  and  later 
known  forms  indicated  by  the  comparative  length  of  skulls  (352-406 
mm) .  The  most  evident  specialization  undergone  during  the  develop- 
ment of  this  genus  is  the  reduction  of  the  sagittal  crest,  the  expansion 
of  the  nasals  distally,  the  strengthening  of  the  squamosal  element  of 
the  arch,  the  appearance  of  incipient  horns  at  the  fronto-nasal  suture, 
the  increase  in  size  of  the  molar  teeth  and  the  relative  reduction  and 
modification  of  the  premolars.  The  incisors  are  so  seldom  preserved 
that  few  deductions  can  be  drawn  from  them.  The  canines,  strong  in 
the  generic  type,  continue  so  in  the  narrower-headed  form,  M .  riparius. 
In  the  broader-headed  species,  M .  cristatus  and  M.  earlei,  the  canines 
become  much  reduced  in  size.  The  post-canine  diastema  is  quite  short 
in  all  species.  P1  is  a  simple  cone  implanted  by  two  roots;  P2  retains 
its  primitive  oblique  position  in  this  series.  P3  and  P4  have  become  sub- 
quadrate  in  outline  and  approach,  in  the  broad-headed  forms,  the 
transverse  position  in  the  series.  The  hypocone  on  M2  which  is  prom- 
inent in  M.  fluviatilis  persists  in  the  later  representatives  of  M.  riparius 

*  Bull.  Amer.  Mus.,  Vol.  XXIV,  p.  610,  1908. 


30    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

but  in  reduced  size.  In  the  broader  headed  M .  cristatus  there  is  a 
trace  of  this  element  but  in  the  later  skulls  of  M.  earlei  it  is  wanting 
entirely.  In  the  lower  dental  series  there  is  a  corresponding  strengthen- 
ing of  M2  and  M3,  a  reduction,  sometimes  a  loss,  of  P1  and  a  slight 
elongation  of  the  post-canine  diastema.  The  Uintah  representatives 
of  this  species  are  somewhat  broader  headed  and  more  massive  than  the 
Bridger  type. 


MEASUREMENTS   OF 

SKULLS   OF   METARHINUS 

IN  MILLIMETERS 


Skull,  length  incisors  to  condyles 

breadth  across  arches 

"        between  orbits 

post-orbital  process  to  condyles 

last  molar  to  condyles 

length  of  free  nasals 

greatest  breadth  of  nasals 

post-glenoids         to         condyles 

(median  line) 

breadth  across  condyles 

greatest  depth  of  arch 

length  of  molar-premolar  series. . 

"      "  molar  series 

"     crown  of  canine 

diameter  crown  of  canine 

length  of  diastema 

narrowest  point  in  sagittal  area 
breadth  of  orbito-nasal  area .... 


>>2 


•  -  3 
I3 

§  d 


352 
205 
112 
214 


107' 


145 

86 


9 
39 


0,0 

"C2 


406 

2I0f 

"4t 

205 

189 

128* 
68 

87 

79 

55 

160 

93 
24 
18 
11 
10 
4i 


a  N 


406 
220' 
107 
212 
193 
115 

68 


82 
51 
155 
93 
29 
20 
10 

39 


15=2 
£ 


3»5: 
240 

145 
215 
195 


90 


92 


4 
43 


5  3 


390 
237 
I37! 
198 

182 


75 

169 
104 


11 

6 
50 


S3 


388 
245 

142 

184 
120 

74 

73 

79 

50 

158 

100 

29 

15 

8 

9 

42 


O  to 


405* 

255* 

220* 
220* 

130* 


80 " 

170 
IO3 

30 
16 
II 
17 
50 


LOWER  JAWS 

">  to 

eg 
2 

03 

•2 

00    TO 

2 

Mandible,  length  condyles  to  incisors. .  . 

height,  condyles  above  angle 

length     of     molar-premolar 

series 

338 
133 

172 
I IO 

34 
21 

52 
60 

330 
125 

162 
102 

32* 
19 

49 
60 

330 
157 

171 
107 

20 

45 
82 

315* 
135 

168 
no 

48 

60 

340 

148 

170 

length  of  molar  series 

crown  of  canine 

diameter  crown  of  canine . . . 
depth  of  ramus  from  base  of 

Pa 

"          depth  of  ramus  from  base  of 
M, 

105 
18 

54 
69 

*Estimated.  fDistorted. 


June,  1912.  New  Titanotheres  —  Riggs.  31 

Dolichorhinus   Hatcher 

Type  species  (D.  cornutus  Osborn)  hyognalhus  S.  &  O. 
Range:  Upper  Bridger,  Washakie  and  Lower  Uintah. 
Original  characterization:*    "Distinguished  from  Manleoceras  and 
Telmatherium  by  the  reduced  number  of  incisors,  presence  of 
incipient  horns,  presence  of  infra-orbital  shelf  and  the  position 
of  posterior  nares." 
Further  knowledge  of  the  genus  has  proved  that  the  reduction  in 
the  number  of  lower  incisors  is  not  constant.     The  genus  may  now  be 
characterized  as  follows: 

Middle  Eocene  titanotheres  progressively  dolichocephalic,  nasals 
elongate  and  laterally  infolded,  cranial  region  strongly  convex, 
incipient  horn-cores  above  the  orbits,  a  shelf -like  infra-orbital 
process,  occiput  broad  and   low,   condyles  broad.     Dentition 
complete,  premolars  relatively  progressive,  first  pair  of  upper 
incisors  separated  by  median  diastema,  posterior  nares  opening 
back  of  last  molars. f     Vertebral  formula:  Cerv.   7,   Dors.    17, 
Lumb.  4,  Sac.  4. 
The  elongate  skull,  440-600  mm.,  with  deeply  recessed  nasals  and 
wide  sagittal  area  strongly  convex  in  the  cranial  region,  everywhere 
distinguishes  this  genus.     The  specimens  examined  by  the  writer  all 
bear  evidence  of  a  recession  of  the  posterior  nares  by  a  secondary  bridg- 
ing of  the  palate.     The  nasals  are  laterally  recessed  to  a  point  over  the 
first  molar.     They  may  be  expanded  in  the  distal  third  or  uniformly 
tapering.     The  infra-orbital  process  is  thickened  and  rugose  at  the 
extremity.     The  median  diastema  between  the  first  pair  of  incisors 
is  a  notch-like  recess  at  the  suture,  varying  from  ten  to  fifteen  milli- 
meters in  breadth.     The  upper  canines  differ  considerably  in  size  and  . 
in  direction,  varying  from  procumbent  to  recurved  types.     The  grind- 
ing teeth  are  longer  in  the  crowns  than  in  any  of  the  other  Lower  Uintah 
titanotheres.     The  last  molar  bears  a  more  or  less  developed  hypocone. 
The  post-glenoid  processes  are  massive  and  elongate  anterio-posteriorly. 

D.  cornutus%  Osborn. 

Type  specimen,  No.  1851  Amer.  Mus. 

Type  locality:  Uintah  B. 

Synonym  J  of  D.  hyognalhus  S.  &  O.  from  Washakie  B. 

*  Amer.  Nat,,  Vol.   XXIX,  p.  1090,  1895. 

t  D.  heterodon  offers  a  possible  exception  to  this  rule. 

§  Bull.  Amer.  Mus.,  Vol.  VII,  p.  90,  1895. 

%  Bull.  Amer.  Mus.,  Vol.  XXIV,  p.  611,  1908. 


32    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

To  the  present  writer  the  abandoning  the  name  of  D.  comulus,  the 
original  type  of  the  genus,  appears  undesirable.  This  species  is  based 
upon  a  well-preserved  skull  with  characteristics  easily  recognizable. 
It  appears  to  the  writer  to  be  a  direct  successor  of  D.  longiceps  which 
is  now  traced  through  the  upper  half  of  Horizon  A  and  lower  Horizon  B . 
The  two  species  apparently  represent  a  line  of  titanotheres  indigenous 
to  the  Uintah  formations.  D.  hyognathus,  with  which  D.  cornutus  has 
been  made  synonymous,  is  a  Washakie  species  based  upon  an  isolated 
mandible.*  No  skull  associated  with  a  similar  mandible  has  been 
described.  The  mandible  indicates  a  much  larger  individual  than  the 
type  of  D.  cornutus.  The  relative  length  of  the  molar-premolar  series 
(208:245  mm.)  in  the  types  of  the  two  species  indicates  a  considerable 
disparity  in  size.  There  are  also  apparent  differences  in  proportions. 
In  view  of  the  variation  in  this  genus  and  the  number  of  species  re- 
ferred to  it,  it  would  appear  unwise  to  correlate  the  two  species  until 
an  associated  skull  and  mandible  referable  to  the  one  or  the  other  species 
is  known. 

D.  intermedius\  Osborn. 

Type  specimen,  No.  1837  Amer.  Mus. 

Type  locality:  Uintah  B  (after  Peterson). 

This  is  apparently  the  smallest  member  of  the  genus  described  from 
the  Uintah  formations.  So  far  as  the  writer  is  able  to  determine,  no 
specimen  in  the  Museum  collection  is  referable  to  this  species. 

1  D.  heterodon\  Douglass. 

Type  specimen,  No.  2340  Carnegie  Museum. 

Type  locality :  Upper  Uintah  B  or  lower  C  (after  Peterson) . 

This  form  as  illustrated  presents  the  characters  of  a  somewhat  spe- 
cialized Dolichorhinus  with  the  posterior  narial  opening  in  the  primary 
position  as  in  Mesatirhinus.  Further  comparison  between  this  species 
and  the  type  of  D.  intermedius  is  needed  in  order  to  determine  their 
relationships. 

D.  longiceps%  Douglass. 

Type  specimen,  No.  12 167  Carnegie  Museum. 

Type  locality :  Uintah  B  (after  Peterson) . 

Four  skulls  (Nos.  12175,  12182,  12193,  12200  Field  Mus.)  collected 
by  the  Museum  expedition  from  the  Upper  Metarhinus  Beds  are  refer- 

*  Scott  &  Osborn,  Trans.  Amer.   Phil.  Soc.  Vol.  XVI,  p.  513.      Earle,  Jour. 
Acad.  Nat.  Sci.  Phila.,  Vol.  IX,  p.  348,  PI.  II. 
t  Bull.  Am.  Mus.,  Vol.  XXIV. 
§  Annals  Carnegie  Mus.,  Vol.  VI,  p.  310. 
%  Op.  cit.,  p.  312,  1909. 


June,  1912.  New  Titanotheres  —  Riggs.  33 

able  to  this  species.  These  specimens  are  somewhat  smaller  and  less 
specialized  than  the  type.  They  vary  in  length  from  525  to  560  mm. 
One  of  the  largest,  a  splendidly  preserved  skull,  is  figured  in  Plate  IX. 
The  canines  as  indicated  by  the  alveoli  of  the  type  are  smaller,  and  the 
premaxillaries  are  somewhat  narrower.  There  is  little  evidence  of 
incipient  horn-cores.  The  nasals  in  this  group  of  skulls  overhang  the 
margin  of  the  premaxillaries.  They  are  laterally  infolded,  slightly 
expanded  in  the  distal  third  and  taper  to  an  emarginate  end.  They  are 
separated  from  the  maxillary  border  by  a  wide  recess.  Compared  with 
D.  intermedins  the  smaller  skull  (No.  12 193)  approaches  closely  in  size, 
the  dental  series  is  similar  in  length,  the  premolars  are  more  advanced, 
and  the  cranial  region  is  more  elongate  in  comparison  with  the  face. 
However,  there  is  a  considerable  variation  in  these  proportions  between 
the  several  individuals  referred  to  this  species.  In  the  palatal  bones 
of  these  specimens  there  is  an  offset  between  the  last  molars  correspond- 
ing to  the  position  of  the  nareal  margin  in  other  closely  related  titano- 
theres. This  is  evidently  a  vestige,  marking  the  former  position  of  the 
narial  opening.  It  has  been  bridged  over  by  the  outgrowth  of  thinner 
plates  from  the  lateral  margin  of  the  palatal  bones  so  that  the  nares  have 
receded  to  appoint  behind  the  hamular  processes  of  the  pterygoids.  The 
plates  of  this  secondary  palate  are  so  thin  that  they  are  often  broken 
through  and  so  the  vestigial  offset  may  be  mistaken  for  the  narial 
margin.  The  secondary  palate  in  this  species  is  pierced  by  a  pair  of 
foramina;  its  posterior  extension  is  an  enfoliate  process  free  from  the 
lateral  walls  and  probably  attached  to  the  inferior  margins  of  the  vomer. 
A  mandible  associated  with  an  incomplete  skull  (No.  12200)  is 
relatively  strong,  curved  in  the  ramus  and  broad  at  the  angle.  (PI.  IX, 
Fig.  2.)  There  is  also  a  large  part  of  a  skeleton  associated  with  this 
specimen  which  is  not  yet  prepared  for  study.  A  detailed  description 
of  this  entire  specimen  will  be  given  in  a  later  publication. 

D.  flutninalis  sp.  nov. 

Type  specimen,  No.  12205  Field  Museum.     (PI.  X,  Figs.  1-3). 

Type  locality:  Amynodon  Sandstone,  Uintah  B. 

Specific  characters:  Skull,  small  and  narrow  (520x230  mm.),  facial 
region  much  shorter  than  cranial,  nasals  narrow  and  slightly 
tapering,  posterior  nares  opening  between  hamular  processes, 
post-orbital  process  of  jugal  back  of  the  last  molar,  molar-pre- 
molar  series  171  mm.;  canines  short  and  recurved,  incipient 
horn-cores  in  the  form  of  high  narrow  ridges. 

This  species  is  represented  by  a  single  splendidly  preserved  skull 
with  almost  complete  dentition,  collected  by  M.  G.  Mehl.     The  skull 


34    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

is  slender,  light  and  complex  in  structure  as  compared  with  the  massive 
and  rounded  D.  cornutus.  The  molar  teeth  are  no  longer  in  the  crown 
than  those  of  Metarhinus  earlei.  The  jugal  process  of  the  maxillaries 
arises  at  a  point  back  of  the  last  molar  rather  than  beside  it  as  in  D. 
longiceps.  There  is  no  offset  in  the  palate  between  the  last  molars, 
though  the  primary  position  of  the  posterior  narial  opening  is  marked 
by  a  slight  rugosity. 

D.  fluminalis  is  most  nearly  related  to  D.  intermedins.  The  skull 
exceeds  in  length  the  type  of  that  species  in  the  ratio  of  520  :  465  mm. 
The  molar  teeth  are  proportionately  much  smaller;  the  series  measures 
relatively  99  :  109  mm.  The  position  of  the  posterior  narial  opening 
is  the  most  distinctive  character,  appearing  much  farther  back  in 
D.  fluminalis  than  in  any  other  described  species.  The  two  forms 
agree  more  closely  in  the  tapering  form  of  the  nasals  and  in  the  narrow 
recess  separating  them  from  the  maxillaries. 


MEASUREMENTS   OF 
DOLICHORHINUS. 
IN    MILLIMETERS 


Skull,  length  incisors  to  condyles 

breadth  across  arches 

"        above  orbits 

post-orbital  process  to  condyles 

last  molar  to  condyles 

length  of  free  nasals 

greatest  breadth  of  nasals 

post-glenoids         to         condyles 

(median  line) 

length  of  molar-premolar  series. . 

"      "   molar  series 

"      crown  of  canine 

diameter  crown  of  canine 

length  of  diastema 

narrowest  point  in  sagittal  area 

breadth  of  orbito-nasal  area .... 

Mandible,  length  condyles  to  incisors . . 

height,  condyles  above  angle 

"         length     of     molar-premolar 

series 

' '         length  of  molar  series 

"       crown  of  canine 

"         diameter  crown  of  canine. . . 
"         depth  of  ramus  from  base 

of  P3 

"          depth  of  ramus  from  base 
of  M3 


•So 


545 : 
260 

310* 

152 
81 


224 
140 


15 
40 


S 


Q   N 


595 

285 


300 


140 
214 

135 
40 
22 
16 


D.  longiceps 
Field  Museum 


550 
247 

134= 
305 
263 
170 
79 

122 
212 
131 

24 
17 
14 
52 


560 : 

255 
130 

305 
280 
i6oJ 


121 
200 
124 


40 
67 


53o 
240 : 

295 

258 


115 
192 
121 

16 
23 
45 


535* 

132 
264 
259 


114 
198 
122 


54 

400 
159 

209 

123 

29 

16 

70 

57 


"is 

a  « 


520 

233 
Il6 


137 

57 


171 

105 

32 

18 

44 


*  Estimated. 


June,  1912.  New  Titanotheres  —  Riggs.  35 

In  its  Uintah  representatives  Dolichorhinus  is  one  of  the  most 
conservative  of  the  titanothere  groups.  Its  greater  specialization 
apparently  occurred  at  an  earlier  date.  The  essential  characters  of 
the  genus  are  well  established  in  the  earliest  known  representatives. 
Within  its  Uintah  range  there  is  comparatively  little  variation  between 
those  individuals  which  may  be  regarded  as  in  the  line  of  sequence. 

D.  longiceps  is  one  of  the  most  common  Uintah  species.  It  occurs 
in  relative  abundance  in  the  upper  half  of  Horizon  A,  less  frequently  in 
Horizon  B.  It  has  a  known  vertical  range  of  700  feet.  In  the  lower 
horizon,  in  the  vicinity  of  Section  1  (Fig.  1)  this  species  was  traced 
through  a  vertical  series  of  400  feet.  The  several  specimens  of  Doli- 
chorhinus collected  from  this  locality  all  belong  to  one  species.  They 
display  some  variation  in  size  and  in  structure.  The  variation  in  size 
is  indicated  by  the  length  of  skulls  in  millimeters  (525-560).  The 
smallest  skull  came  from  the  top  of  the  series,  a  larger  one  from  near 
the  base.  There  is  a  more  noticeable  variation  in  the  size  of  canines, 
breadth  of  the  premaxillary  region  and  of  the  sagittal  area.  (See  table 
of  measurements.)  These  differences  are  evidently  due  in  a  great 
measure  to  sex.  The  type  specimen  described  from  Horizon  B  is  similar 
in  size  to  the  larger  specimens  from  Horizon  A.  The  premaxillaries 
are  broad,  the  alveolus  indicates  larger  canines.  In  the  development 
of  horn-cores  this  species  is  less  advanced  than  any  other  of  the  genus. 
There  is  a  rounded  angle  over  the  eye  in  the  vicinity  of  the  fronto-nasal 
suture,  but  in  no  specimen  observed  is  there  a  prominent  excrescence 
or  rugosity. 

The  type  specimen  of  D.  cornutus*  is  a  somewhat  more  highly  spe- 
cialized form  than  D.  longiceps.  This  specialization  appears  in  the 
greater  breadth  of  the  supra-cranial  area,  in  the  more  highly  developed 
horn-cores,  and  the  elongation  of  the  cranial,  as  compared  with  the 
facial,  region.  At  the  same  time  there  are  those  elements  of  similarity 
between  the  two  which  suggest  a  common  stock.  The  present  writer 
would,  therefore,  regard  the  type  of  D.  cornutus  as  a  more  advanced  stage 
of  the  phylum  which  includes  D.  longiceps.  This  appears  to  be  an  indi- 
genous line  extending  through  the  greater  part  of  the  Lower  Uintah  series. 

The  species  D.  heterodon  and  D.  fluminalis  must  be  regarded  as 
aberrant  forms.  The  former  species  as  figuredf  shows  no  indication 
of  the  backward  shifting  of  the  posterior  nares  so  characteristic  in 
other  species  of  the  genus.  If  this  figure  of  the  nares  is  correct  the 
great  convexity  in  the  supra-cranial  region  is  the  chief  distinction 
between  this  form  and  Mesatirhinus  superior.     The  position  of  the  nares 

*  Bull.  Amer.  Mus.,  Vol.  VII,  p.  90. 

t  Annals  Carnegie  Mus.,  Vol.  VI,  p.  310. 


36    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

would  designate  D.  heterodon  as  a  primitive  form ;  the  position  assigned 
to  it  geologically  indicates  that  it  is  the  most  recent  yet  described.  It 
is  apparently  one  of  those  rare  forms,  immigrants  or  adaptations  under 
stress,  which  characterize  the  transitional  stage. 

D.  fluminalis  displays  a  high  degree  of  specialization  in  the  post- 
narial  characters.  The  nares  are  bridged  over  so  as  to  obliterate 
almost  all  evidence  of  their  primary  position.  In  this  process  the 
opening  has  receded  to  a  point  back  of  the  hamular  processes. 
This  recession,  noted  in  less  degree  in  other  species,  is  evidence  of  a 
secondary  adaptation  to  aquatic  habits  of  feeding.  Other  characters 
of  the  skull  in  this  species  would  not  indicate  that  this  animal  was 
aquatic  in  its  general  habits.  Like  many  other  terrestrial  mammals 
it  probably  fed  upon  submerged  plants.  The  slenderness  and  delicate 
modeling  of  the  skull  would  suggest  an  animal  lighter  of  limb  and 
more  active  than  other  species  of  this  genus.  In  the  development  of 
horns  the  type  of  this  species  is  more  advanced  than  the  type  specimen 
of  D.  cornutus.  Its  narrower  sagittal  area,  its  strongly  recurved  canines 
and  much  smaller  molars  readily  distinguish  it  from  that  species. 

Rhadinorhinus  gen.  nov. 

Type  species:   R.  abbotti. 

Range:  Metarhinus  Beds,  Middle  Eocene. 

Generic  characters:  Titanotheres  with  slender  skulls,  nasals  deeply 
recessed  laterally  and  tapering,  molars  long-crowned,  P2,  3,  4,  sub- 
rectangular,  a  wide  median  area  between  the  incisors,  no  infra-orbital 
process.  The  name  "Rhadinorhinus"  alludes  to  the  tapering  nasals 
which  characterize  this  genus. 

R.  abbotti,  sp.  nov. 

Type  specimen,  No.  12 179  Field  Museum.      (PL  XI,  Figs.  2-3). 
Type  Horizon:   Upper  Metarhinus  Beds. 

Specific  characters:  Length  of  skull  435  mm.,  molar-premolar  series 

168  mm.,  nasals  shorter  than  premaxillaries,  thickened  at  suture 

and   tapering   toward    a    terminal    rugosity.     Arches   slender, 

posterior  nares  open  opposite  middle  of  M2.     Sagittal  crest  long 

and  narrow.  .  Hypocone  of  M3  vestigial,  diastema  short. 

This  interesting  specimen  was  discovered  by  Mr.  J.  B.  Abbott,  in 

whose  honor  it  is  named.     It  indicates  a  form  closely  related  to  both 

Mesatirhinus  and  Metarhinus,  but  probably  differing  from  them  in 

habits.     The  skull  is  slighter  in  construction,  the  arches  more  slender 

and  the  teeth  longer  in  the  crowns  throughout.     The  frontal  region  is 


June,  1912.  New  Titanotheres —  Riggs.  37 

rounded,  the  post-orbital  process  elongate.  The  nasals  are  convex 
on  the  inferior  surface  owing  to  the  thickening  at  the  sutural  line. 
The  molar  teeth  are  long  in  the  crown  having  inner  cones  nearly  equal 
in  height  to  the  ectoloph.  The  molar-premolar  series  is  well  preserved 
and  unworn  in  the  type  specimen.  The  canines  are  broken  at  the 
alveolus;  half  of  the  incisors  are  preserved.  The  dentition  as  a  whole 
is  more  highly  specialized  than  that  of  Metarhinus.  The  first  and 
second  incisors  have  short,  rounded,  semi-conical  crowns  indented  by 
cups  on  the  posterior  surface.  The  third  incisor  has  a  more  elongate 
crown  (23  mm.),  the  cup  is  suggested  by  a  prominent  cingulum  on  the 
posterior  margin.  An  interval  of  six  millimeters  separates  the  third 
incisor  from  the  canine.  The  latter  is  eighteen  millimeters  in  diameter 
and  circular  at  the  alveolar  section.  The  elongate  third  incisor  would 
indicate  a  long-crowned  canine.  The  first  premolar  is  a  simple,  blunt 
cone  with  an  internal  cingulum  and  emplanted  by  two  roots.  Pre- 
molars 2,  3,  4  increase  steadily  in  length  of  ectoloph  and  deuterocone; 
strong  internal  cingula  persist.  The  last  three  have  taken  on  the  sub- 
rectangular  outline  indicating  a  stage  in  dental  specialization  similar 
to  that  of  Sthenodedes.  The  molars  are  long-crowned ;  the  protocone 
increases  steadily  in  height  from  first  to  third.  The  hypocone  is  more 
prominent  in  the  second  and  reduced  to  a  vestige  in  the  cingulum  of  the 
third.  The  entire  molar-premolar  series  is  more  curved  than  in  any 
other  Uintah  titanothere. 

In  its  general  proportions  the  skull  of  R.  abbotti  is  similar  to  that 
of  Metarhinus  riparius.  Somewhat  longer  and  more  slender  in  the 
arches,  the  skull  suggests  a  longer-limbed  and  more  active  animal. 
The  facial  and  palatal  aspects  differ  more  widely.  The  anterior  narial 
opening  is  high  and  the  nasals  are  not  infolded  at  the  base.  They 
terminate  above  the  anterior  margins  of  the  canines.  There  is  no 
antorbital  fossa,  the  muzzle  is  broad  and  the  canines  evidently  elongate. 

R.  diploconus. 

Type  specimen  Telmatotherium  diploconum  Osborn. 

Horizon:  Uintah  Metarhinus  Beds. 

This  species  should  be  removed  from  Metarhinus  because  of  the 
highly  specialized  dentition  associated  with  a  narrow  sagittal  crest  and 
the  absence  of  an  infra-orbital  process.  The  absence  of  the  nasals  from 
the  type  specimen  leaves  its  affinities  somewhat  in  doubt.  Until  these 
shall  be  known  it  is  proposed  to  refer  the  species  to  Rhadinorhinus. 
It  differs  from  R.  abbotti  in  having  a  more  concave  profile,  somewhat 
larger  molars  and  a  well-developed  hypocone  on  M3. 


38    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

Sthenodectes   Gregory 

This  generic  name  has  recently  been  applied*  to  a  form  of  short- 
headed,  massive-jawed  titanothere  known  from  the  Amynodon  Beds 
(Horizon  B)  of  the  Uintah.  So  far  only  three  specimens  have  been 
recorded,  all  of  which  are  from  the  same  locality  and  belong  to  the  same 
species. 

A  skull  (No.  1 2165)  and  a  pair  of  lower  jaws  (No.  1 2166)  are  included 
in  the  Field  Museum  collection.  They  were  discovered  by  Mr.  Abbott 
in  the  lenticular  sandstones  near  Well  2  at  the  foot  of  Coyote  Basin. 
The  skull  (PI.  XII,  Figs.  1-2)  is  shorter  then  the  type  of  S.  incisivum  but 
has  the  broad,  low-crowned  molars  and  massive  incisors  of  that  species. 
At  approximately  the  same  level  and  a  half  mile  distant  was  found  the 
mandible  referred  to  this  species.  (PL  XII,  Fig.  3.)  It  belongs  to  an 
older  individual,  as  is  evident  from  the  worn  molars  and  incisors.  The 
crowns  of  the  incisors  are  almost  worn  away.  The  mandible  is  ten 
millimeters  shorter  than  would  be  required  to  fit  the  skull,  but  the 
dentition  matches  closely.  The  molars  have  the  strength  necessary  to 
oppose  the  massive  upper  series ;  the  canines  and  incisors,  though  not  so 
massive  as  those  above,  show  such  wear  as  would  be  expected  in  this 
form.  The  canines  are  worn  away  diagonally  at  the  point  of  contact 
with  the  third  upper  incisor,  but  very  little  from  contact  with  the  upper 
canines.  There  is  a  short  diastema  between  canines  and  premolars. 
The  mandible  as  a  whole  is  titanothere-like  —  deep  through  the  ramus, 
broad  at  the  angle,  concave  in  the  tooth-line  and  tapering  toward  the 
anterior  extremity.     The  coronoid  is  short  and  recurved  at  the  tip. 

*  Science,  Vol.  XXXV,  p.  546. 


June,  1912. 


New  Titanotheres  —  Riggs. 


39 


MEASUREMENTS   OF 
RHADINORHINUS,    MESATIRHINUS   AND 
STHENODECTES   IN 
MILLIMETERS 


Id 

•5H.E 

o  « 


£2 

a 


ft!2 


■-  >>E 


£5 


a  5 


2 


5  o 

IE 
•5  £ 

00H 


5S 

•5  ° 

5S 


Skull,  length  incisors  to  condyles 

breadth  across  arches 

"        between  orbits 

post-orbital  process  to  condyles 

last  molar  to  condyles 

length  of  free  nasals 

greatest  breadth  of  nasals 

post-glenoids    to    condyles    (median 

line) 

breadth  across  condyles 

greatest  depth  of  arch 

length  of  molar-premolar  series 

"       "  molar  series 

"      crown  of  canine 

diameter  crown  of  canine 

length  of  diastema 

narrowest  point  in  sagittal  area 

breadth  of  orbito-nasal  area 


LOWER  JAWS 

Mandible,  length  condyles  to  incisors 

height,  condyles  above  angle 

length  of  molar-premolar  series .  . 

length  of  molar  series 

"     crown  of  canine 

diameter  crown  of  canine 

depth  of  ramus  from  base  of  Pm.  * 
depth  of  ramus  from  base  of  M  3 .  . 


426 
224 

134 
240 
196 
102 


88 

84 

38 

164 

103 


7 

4 

46 


440 
210' 

262 


82  < 

172 
no 

15 
6 

47 


435 
215 
115 
220 
210 
95 


165 
105 

20* 
10 


585 
240 
120 
276 
260 
138 
68 


36 

184 

105 

23 

18 

15 
26 

52 


305 
170 
261 
197 

64 

74 
89 

271 

130 

56 

25 

o 

94 


460 
300 
160 
262 
190 


86 
101 

211 

132 

47 

27 
o 


vO  3 

as 

6~v 
2£ 

360 

168 

215 
130 
30" 

19 
60 

84 


*  Estimated. 


40    Field  Museum  of  Natural  History  —  Geology,  Vol.  IV. 

GENERIC   RELATIONSHIPS 

Under  the  subfamily  Dolichorhince  are  included  four  genera  which 
have  in  common  the  characteristics  before  designated.  They  are  in 
general  low  ground  or  river  forms  although  certain  species  suggest  active 
habits.  In  most  instances  they  bear  evidence  of  incipient  horn  develop- 
ment but  it  is  doubtful  if  any  of  these  forms  became  true  horn-bearing 
titanotheres.  So  far  as  is  now  known  they  die  out  with  the  close  of  the 
Washakie  and  the  beginning  of  the  Upper  Uintah.  However,  there 
remains  much  to  be  learned  of  the  titanotheres  in  their  Upper  Eocene 
development. 

The  most  primitive  genus  included  in  this  group  is  Mesatirhinus. 
This  is  evident  from  the  molar  and  premolar  pattern,  the  oblique 
position  of  the  premolars  in  the  series  and  the  structure  of  the  nasal 
and  frontal  region.  The  latter  characters  show  affinities  with  Palce- 
osyops  to  which  group  the  type  species  was  first  referred.  Mesatirhinus 
may  therefore  be  regarded  as  standing  in  an  ancestral  relation  to  the 
other  members  of  this  subfamily,  though  there  is  little  evidence  that 
it  actually  gave  rise  to  any  of  them.  The  relationships  of  the  Bridger 
and  Washakie  members  of  the  genus  do  not  come  within  the  province 
of  this  paper. 

Metarhinus,  as  has  already  been  observed,  may  be  regarded  as  in- 
digenous to  the  Uintah  Basin.  Its  type  specimen  is  the  earliest  mammal 
from  this  formation  whose  relationships  have  been  determined.  It 
attains  a  wide  dispersal  and  becomes  the  most  characteristic  fossil  in 
the  lower  subdivision  of  the  Uintah  Series.  This  genus  in  its  most 
primitive  Uintah  representative  is  not  far  removed  from  the  type  and 
most  primitive  species  of  Mesatirhinus.  As  near  as  may  be  determined 
from  the  present  limited  knowledge  of  the  lowermost  Uintah  fauna,  the 
two  type  species  are  nearly  contemporary.  Mesatirhinus  appears  to  be 
indigenous  to  the  Bridger  and  Washakie  basins,  Metarhinus  to  the 
Uintah.  Each,  in  its  later  development,  is  represented  in  the  other's 
native  formation  by  an  immigrant  species. 

While  the  types  of  these  two  genera  are  similar  in  size  and  nearly 
contemporary,  Metarhinus  is  in  many  ways  more  highly  specialized. 
The  dentition  is  more  advanced  in  the  general  trend  of  titanothere 
specialization,  the  nasal  and  facial  region  is  likewise  more  specialized. 
On  the  contrary  it  retains  in  the  high  sagittal  crest  an  equally  primitive 
character  which  the  most  advanced  species  have  not  quite  eliminated. 

Dolichorhinus  appears  suddenly  in  the  Lower  Uintah  Series  as  a 
highly  differentiated  form.     It  is  earliest  reported*  from  the  Washakie 

*  Earle,  Osborn  Op.  cit. 


June,  1912.  New  Titanotheres  —  Riggs.  41 

formation  of  a  somewhat  later  stage  and  as  an  even  more  highly  spe- 
cialized form.  It  is  thus  a  successor  to  Mesatirhinus  in  its  geological 
range  (Fig.  1),  though  D.  longiceps  occurs  abundantly  in  the  Uintah 
formation  at  a  level  400  feet  below  the  horizon  from  which  the  occur- 
rence of  Mesatirhinus  superior  is  recorded.  Members  of  these  two 
species,  though  similar  in  size,  have  less  in  common  than  has  the  latter 
with  D.  heterodon  of  a  later  stage.  These  similarities  are  sufficient  to 
suggest  that  Dolichorhinus  probably  sprang  from  some  earlier  and  less 
specialized  form  of  Mesatirhinus.  The  differentiations  of  the  former 
may  well  have  arisen  with  its  adaptation  to  aquatic  habits. 

Rhadinorhinus  apparently  represents  a  side  branch  from  the  early 
Metarhinus  stem.  The  facial  and  cranial  regions  and  the  zygomata 
are  similar.  The  nasals  indicate  an  early  specialization  in  another 
direction.  The  dentition  is  more  highly  specialized  than  that  of  Doli- 
chorhinus and  in  some  respects  resembles  it.  The  posterior  nares  open 
a  little  farther  forward  than  those  of  Metarhinus.  The  mere  trace  of 
an  infra-orbital  process  also  removes  it  somewhat  from  the  long-nosed, 
low-ground  titanotheres. 

The  broad-headed  genus  Sthenodectes  appears  in  Horizon  B  as  a  well 
differentiated  form.  Its  highly  developed  dental  structure,  short 
cranium  and  nasals  offer  only  distant  relationships  with  the  more 
common  Lower  Uintah  titanotheres.  It  would  fall  into  another  sub- 
family which  should  include  the  short-nosed,  heavy-toothed  forms  which 
were  evidently  ancestors  of  the  true  horned  titanotheres. 

r 

ACKNOWLEDGMENT 

In  the  preparation  of  this  publication  Professor  Osborn  has  accorded 
the  writer  the  freest  access  not  only  to  the  type  specimens,  but  also 
to  the  entire  series  of  titanothere  collections  brought  together  at  the 
American  Museum  in  the  preparation  of  his  forthcoming  monograph 
on  the  Titanotherida?.  Dr.  W.  K.  Gregory  of  the  same  Museum  has 
given  most  valuable  assistance  in  making  comparisons  and  in  furnishing 
unpublished  data  from  these  collections  in  order  to  facilitate  identifica- 
tions. Mr.  O.  A.  Peterson  of  the  Carnegie  Museum  has  also  furnished 
unpublished  data  from  his  field  observations  in  regard  to  faunal  horizons 
and  other  aids  in  establishing  stratigraphic  subdivisions.  For  these 
courtesies  and  aid  the  writer  wishes  to  acknowledge  his  obligations. 


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Explanation  of  Plate  V 

UPPER  FIGURE 

Green  Clays  capped  by  Amynodon  Sandstone.     Exposed  at  the  northern  bounda- 
ry of  Coyote  Basin. 

LOWER  FIGURE 

Fossil-bearing  sandstone,  Upper  Metarhinus  Zone,  exposed  on  the  divide  betweer 
White  River  Canyon  and  Coyote  Basin,  in  the  vicinity  of  Section  2. 


FIELD  MUSEUM  OF  NATURAL  HISTORY. 


GEOLOGY,  VOL.  IV,  PL.  V. 


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u:::a:;.\ 


Explanation  of  Plate  VI 


Mesatirhinus  superior,  sp.  nov.,  page  26. 
Fig.  1.     Side  view  of  skull,  type  specimen. 
Fig.  2.     Top  view  of  same. 
Fig.  3.     Palate  view  of  same. 


FIELD  MUSEUM  OF  NATURAL  HISTORY. 


GEOLOGY,  VOL.  IV,  PL.  VI. 


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Explanation  of  Plate  VI I 

Metarhinus  riparius  sp.  nov.,  page  28. 
Fig.  1.     Side  view  of  skull,  type  specimen. 
Fig.  2.     Upper  view  of  jaws,  cotype. 
Fig.  3.     Side  view  of  same. 


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GEOLOGY,  VOL.  IV,  PL.  VII. 


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EXPLANATION  OF  PLATE  VIII 

Metarhinus  earlei,  Osborn. 
Fig.  I.     Side  view  of  skull  No.  12187,  Field  Museum. 
Fig.  2.     Top  view  of  same. 
Fig.  3.     Palate  view  of  same. 


FIELD   MUSEUM  OF  NATURAL  HISTORY. 


GEOLOGY,  VOL    IV,  PL.  VIII. 


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EXPLANATION  OF  PLATE   IX 

Fig.  i.     Side  view,  skull  of  Dolichorhinus  longiceps,  No.  12175,  Field  Museum. 
Fig.  2.     Lower  jaw  of  D.  longiceps,  No.  12200,  Field  Museum. 
Fig.  3.     Skull  of  Metarhinus  cristatus,  sp.  nov.,  page  28. 


FIELD  MUSEUM  OF  NATURAL     HISTORY. 


GEOLOGY,  VOL.  IV,  PL.  IX. 


V 


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Explanation  of  Plate  X 

Dolichorhinus  fluminalis  sp.  nov.,  page  33. 
Fig.  1.     Side  view  of  skull,  type  specimen. 
Fig.  2.     Top  view  of  same. 
Fig.  3.     Palate  view  of  same. 


FIELD  MUSEUM  OF  NATURAL  HISTORY. 


GEOLOGY,  VOL.  IV,  PL.  X. 


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URBANA 


EXPLANATION  OF  PLATE  XI 

Fig.  i.     Lower  jaw  of  Metarhinus  earlei  No.  12178,  Field  Museum. 
Fig.  2.     Skull  of  Rhadinorhinus  abbotti,  page  36. 
Fig.  3.     Top  view  of  same. 


FIELD  MUSEUM   OF  NATURAL  HISTORY. 


GEOLOGY,  VOL.  IV,  PL.  XI. 


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UR3ANA 


Explanation  of  Plate  XII 

Sthenodectes  incisivum,  Douglass. 
Fig.   i.     Side  view  of  skull  and  jaws. 
Fig.  2.     Palate  view  of  skull,  No.  12168,  Field  Museum. 
Fig.  3.     Upper  view  of  jaws,  No.  12 166,  Field  Museum. 


FIELD  MUSEUM  OF  NATURAL  HISTORY.  GEOLOGY,  VOL.  IV,  PL.  XII. 


